Pressure inducing charge

ABSTRACT

A charge assembly for incorporation into a downhole tool to induce pressure at an interior of the tool during a downhole application. The assembly includes a reactive powder metals that is particularly configured of a reaction rate slower than that of a high energy explosive directed at the application. Thus, upon triggering of the explosive and downhole application in a high pressure well environment, reaction of the powder metals may serve to substantially reduce any pressure differential at the tool. As such, shock related damage due to sudden introduction of pressure differential wave to the tool may be minimized.

BACKGROUND

Exploring, drilling and completing hydrocarbon and other wells are generally complicated, time consuming and ultimately very expensive endeavors. As a result, over the years well architecture has become more sophisticated where appropriate in order to help enhance access to underground hydrocarbon reserves. For example, as opposed to wells of limited depth, it is not uncommon to find hydrocarbon wells exceeding 30,000 feet in depth. Furthermore, as opposed to remaining entirely vertical, today's hydrocarbon wells often include deviated or horizontal sections aimed at targeting particular underground reserves.

While such well depths and architecture may increase the likelihood of accessing underground hydrocarbons, other challenges are presented in terms of well management and the maximization of hydrocarbon recovery from such wells. For example, during the life of a well, a variety of well access applications may be performed within the well with a host of different tools or measurement devices. However, providing downhole access to wells of such challenging architecture may require more than simply dropping a wireline into the well with the applicable tool located at the end thereof Indeed, a variety of isolating, perforating and stimulating applications may be employed in conjunction with completions operations.

In the case of perforating, different zones of the well may be outfitted with packers and other hardware, in part for sake of zonal isolation. Thus, wireline or other conveyance may be directed to a given zone and a perforating gun employed to create perforation tunnels through the well casing. As a result, perforations may be formed into the surrounding formation, ultimately enhancing recovery therefrom.

The described manner of perforating can be accompanied by a significant degree of ‘gun shock’, particularly in higher pressure wells. That is, in conjunction with firing of perforating gun, a problematic pressure wave may arise from differential pressure which then results in undesired movement of the gun and associated equipment inside the wellbore. This may result in damage to the well and surrounding hardware. For example, the perforating shaped charges are initially held within a carrier of the gun that is of a given ambient pressure which is isolated from the pressure of the well. Once the gun is fired, the detonation pressure forms inside the gun carrier while the shape charge jets emerge from the carrier in a manner that creates holes within the wall of the carrier. The differential between the post-detonation pressure within the carrier and that of the well can lead to a sudden rush of wellbore fluids into (or a sudden rush of detonation gas products out of) the carrier depending on whether the detonation pressure inside the gun carrier is smaller or larger than the wellbore pressure. Strong pressure waves may be induced by this rapid fluid motion. Thus, gunshock results. A large magnitude of the pressure wave can damage the downhole equipment.

As well environments continue to become harsher and depths continue to increase, the degree of gunshock may be quite significant. For example, while the gun and carrier are sealed at surface, the pressure at the high pressure well zone at issue may be anywhere from 10,000 to 25,000 PSI. Thus, a dramatic degree of gunshock may follow a firing perforating application. This may damage surrounding hardware at the zone and require follow-on remediation. Ultimately, the loss of operational time and cost of hardware repair or replacement may run in the hundreds of thousands of dollars if not more.

So as to help avoid such significant expense, efforts have been undertaken as a means of addressing the issue of gunshock. For example, metal-based filler may be distributed throughout the inner volume of the carrier. As a result, once perforating takes place and the carrier is exposed to the surrounding well pressure, the degree of gunshock may be minimized due to the small amount of lower pressure space actually exposed. Of course, this also results in a heavier and more expensive gun.

As an alternative to the heavier metal-filled carrier housing, measures may be undertaken which address the nature of underlying perforating application reactions themselves. For example, perforating by firing a series of shaped charges as noted above are detonated by detonation cord. Thus, the detonation of each charge leads the high speed jet that creates the perforation. In order to address gunshock as noted above, the charges may alternatively include propellant to increase gas production after the firing. In theory, the slower reacting propellant would lead to pressure increase inside perforating gun following the detonation of shaped charge,

Unfortunately, propellants which might theoretically be of limited effectiveness in this manner often fall short in the reality of the well environment. That is, these propellants are not particularly well suited to withstand high temperature environments which are often high pressure as described hereinabove. Thus, a more effective technique is needed to mitigate the gun shock damage.

SUMMARY

A charge for use with downhole tools such as a perforating gun is disclosed. The charge may be located within a carrier housing of the tool and equipped with different types of explosives. For example, a first type of explosive may be incorporated into the charge for carrying out an application in a well such as perforating. However, a second type of explosive such as reactive metal powder may be incorporated into the charge for adjusting (or controlling) a pressure differential between the well and the carrier housing immediately after the application.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side partially sectional view of an embodiment of pressure inducing charge assembly incorporated into a perforating gun.

FIG. 2A is an enlarged view of an embodiment of a pressure inducing charge of the assembly of FIG. 1.

FIG. 2B is an enlarged view of another embodiment of the pressure inducting charge assembly of FIG. 1.

FIG. 3 is an overview of an oilfield with a well thereof accommodating the perforating gun of FIG. 1 for a perforating application therein.

FIG. 4A is an enlarged view of the gun in the well of FIG. 3 in advance of a perforating application.

FIG. 4B is an enlarged view of the gun in the well of FIG. 3 upon perforating therewith.

FIG. 4C is an enlarged view of the gun in the well of FIG. 3 following the noted perforating.

FIG. 5 is a flow-chart summarizing an embodiment of utilizing a pressure inducing charge assembly in a well.

DETAILED DESCRIPTION

Embodiments are described with reference to certain perforating applications directed at high pressure well environments. In particular, wireline deployed perforating gun applications are detailed. However, other forms of deployment and application types may take advantage of pressure inducing charge embodiments as detailed herein. Regardless, pressure inducing charge assemblies are described which include a metal reactive powder material for minimizing a pressure differential between the assembly and surrounding well pressure at the time of the application.

Referring now to FIG. 1, a side partially sectional view of an embodiment of a gun assembly 101 is depicted. The assembly 101 is of pressure inducing capacity and may take a variety of different configurations. Additionally, the assembly 101 includes an outer housing or carrier 150 for structurally retaining a variety of shaped charges 125. More specifically, the charges 125 may include a variety of different uniquely configured shaped charge holder 100. For example, in the embodiment shown, a highlighted shaped charge 125 in a charge holder 100.

A detonation cord 140 is provided to each of the indicated shaped charges 125 to allow for detonation or firing during a perforating application (e.g. such as within the well 180 depicted in FIG. 3). Additionally, void space 130 within the carrier 150, may be of a given pressure that is likely well below surrounding pressure of a well 180. That is, the entire gun assembly 101 may be deployed within a well 180 of potentially significant pressures, perhaps well in excess of 10,000 PSI. However, the noted void space 130 may be no more than the standard atmospheric pressure at the oilfield surface 301. Thus, a substantial pressure differential is presented at either side of the carrier wall 175. However, as alluded to above and detailed further below, the various shaped charges 125 may be constructed in a manner that avoids significant gun shock even in the face of such significant differentials.

Continuing with reference to FIG. 1, the noted charge holders 100 are configured to provide a condition of overpressure upon firing of each corresponding shaped charge 125. More specifically, this may take place as a gas is generated in conjunction with the firing such that the above described pressure differential is actually minimized as the firing takes place. As a result, gunshock is accordingly minimized due to reduced differential pressure.

The above described embodiments include holders 100 which may be self-contained devices that provide structural support for accommodation of a material 190 therein which may be in the form of a reactive metal powder. Alternatively, the reactive metal powder may be incorporated into the case 195 or elsewhere. As described further below, the reactive metal powder material may be a powder mixture of heat and gas generating constituents of a generally slower reaction rate than that of the high energy explosive in conventional shaped charge. For example, the detonation cord 140 may initially set off high energy explosives in the shaped charge 125 for sake of perforating. However, this may in turn lead to initiating a reaction of reactive metal powder of material types as detailed further below. This subsequent reaction of reactive metal powders may take place at a rate thousands to millions of times slower than the initial reaction of high energy explosive. Yet, by taking place in this sequential and subsequent manner, heat and gas buildup emerges in a manner to diminish the above detailed pressure differential.

The particular construction of the shaped charges 125 may be configured in light of likely exposure to higher temperature and pressure environments. Further, apart from driving a perforating shaped charge jet as described below, a shaped charge 125 as detailed herein may additionally or alternatively drive the generation of heat and/or gas sufficient to diminish pressure differentials. In fact, with such capacity provided to the gun assembly 101, it may be effectively employed in even higher pressure wells without undue concern over downhole architectural damage as a result of extensive gunshock. Indeed, substantial gunshock related damage may be avoided through use of embodiments as described herein, even in circumstances where the targeted downhole location of the well 180 exceeds about 20,000 PSI.

Referring now to FIGS. 2A-2B, enlarged views of different embodiments of the pressure inducing shaped charges 125 of FIG. 1 are depicted. More specifically, FIG. 2A depicts a charge mechanism that is configured to address pressure inducement as described above as it directs a jet 425 during a perorating application as shown in FIG. 4B. FIG. 2B, however, reveals a shaped charge 125 that is dedicated to driving up pressure within the carrier space 130 without a corresponding fired jetting 425 or exposing of the space 130 to the well 180 of FIGS. 1 and 3.

With specific reference to FIG. 2A, the ignition line 140 reaches the shaped charge 125 for firing. The charge 125, and firing thereof, take place within the void space 130 defined by the carrier 150 of FIG. 1. In the embodiment of FIG. 2A, the initial firing is in the form of setting off of the material 190 held within the case 195 of the charge 125. More specifically, a jet 425 as depicted in FIG. 4B may be explosively discharged from the shaped charge 125 for sake of perforating as detailed further herein. In the embodiment of FIG. 2A, a conical shaped liner 201 forms the noted jet 425.

Upon firing of the high energy explosive that makes up the material 190 as described above, a secondary reaction may also be initiated. More specifically, the case 195 itself may be constructed of a reactive metal powder having a comparatively slower reaction rate as noted hereinabove. Thus, in conjunction with the initial high energy explosive reaction, a subsequent gas forming reaction is ignited which takes place over a longer period of time so as to increase pressure in the depicted void space 130. As such, gunshock inducing pressure differentials may be minimized.

In one embodiment, the heat and gas forming reaction of the material may be one that is fuelled by a mixture of at least about 5% of each of a metal, a metal oxide or/and metal nitrate, a metal carbonate. That is, the case 195 may be constructed of a powder form of such materials, compressed into a durable form so as to make up the structure of the case 195. With added reference to more specific material choices below, in one embodiment, the case 195 may be constructed of a mixture of Al, Fe₂O₃, CaCO₃, and Ca(NO₃)₂. Thus, during this subsequent or extended reaction a generation of carbon oxide and nitrate gases may ensue so as to mitigate the pressure differential and any measurable degree of gunshock. Once more, this mitigation may take place over a longer period of time as compared to the initial primary reaction, thereby provided an added degree of mitigation.

The particular reactive metal powder material of the case 195 may be any of, or a combination of, aluminum, beryllium, titanium, tantalum, yttrium, and/or zirconium. As for metal oxides, bismuth, cobalt, chromium, copper, iron, iodine, manganese, nickel, lead, strontium, and tungsten-based oxides may be utilized. Metal carbonates of barium, calcium, magnesium, potassium, lithium and/or a strontium-base may be employed which, during reaction may degenerate to carbon dioxide gas. Similarly, the metal nitrate may lead to the generation of a gas. Candidates of this nature may include a nitrogen-oxide based barium, calcium, lithium, potassium magnesium and/or strontium.

In another embodiment, the material types of the case 195 and internal material 190 may be reversed. That is, the case 195 may be constructed of the high energy explosive for fueling the perforating, whereas the internal material 190 may be of an extended reacting, reactive metal powder form. Indeed, for that matter, a liner 201 of reactive metal powder, may also be provided to further fuel the appropriate reaction.

In yet another embodiment, the entire charge 125 may be filled with an internal material 190 of only the reactive metal powder. That is, with added reference to FIGS. 1, and 4A-4C, a host of charges 125 may be provided. However, some may be fully dedicated to gas generation via secondary reactions whereas others are configured for perforating. In the embodiment of FIG. 2B, a charge 125 dedicated to increased pressurization of the carrier space 130 is depicted. Thus, as opposed to directional cavity 200 for a jet 425, a pure metal steel, zinc or other inert metal case 195 may be filled with almost entirely with material 190 in the form of reactive metal powder. Although in the embodiment shown, an ignition substrate 245 of primary reaction material may be provided that is in communication with the ignition line 140. Thus, the metal powder reaction may be triggered sufficiently for exposure of the noted void space 130, through the case 195.

Referring now to FIG. 3, an overview of an oilfield 301 is depicted with a well 180 accommodating an embodiment of the perforating gun assembly 101 of FIG. 1 disposed therein for sake of a perforating application. Thus, during perforating of the well wall (e.g. at adjacent casing 480), the degree of gun shock may be minimized More specifically, as detailed hereinabove, the pressure differential between the well 180 and internal space of the gun assembly 101 may be diminished through the use of pressure inducing charges 125 (see FIGS. 1 and 2A-2B). As a result, hardware such as the adjacent packer 325, casing 480 and other potential structure may avoid any significant damage from sudden dramatic shifting and jumping or swaying of the gun assembly 101 in response to perforating/firing thereof.

Continuing with reference to FIG. 3, the particular application depicted is one of perforating as described above. However, use of a pressure inducing charge assembly 101 for sake of diminishing pressure differentials during an application may be employed for a variety of downhole uses. Once more, the perforation application utilizes wireline 330 for deployment, though tubing, coiled tubing and other deployment techniques may also be utilized. As shown, a mobile wireline truck 310 with conventional drum 340 is positioned at the oilfield surface 301 adjacent a rig 350. The rig 350 is positioned over the well head 375 for vertical suspension and delivery of the gun assembly 101 through the well 180 and across various formation layers 395, 495. Ultimately, the target location for perforating is reached as depicted. In the embodiment shown, isolation with a packer 325 is achieved in advance of perforating. Thus, other zones further downhole are left largely substantially unaffected by the application. However, in other embodiments, no packer 325 may be used or alternatively, multiple packers 325 may be used, with one at either side of the target location.

Referring now to FIGS. 4A-4C, enlarged views of the perforating gun assembly 101 are depicted within the well 180. More specifically, the gun assembly 101 is shown at the target location before, during and immediately after a perforating application.

With specific reference to FIG. 4A, the gun assembly 101 is shown located at the target location in advance of perforating. As alluded to above, the target location lies adjacent casing 480 which defines the well 180 and serves as a border to the formation 495 that is to be perforated. Additionally, in this embodiment, the gun assembly 101 includes a pressure inducing charge assembly 101 that employs charges 125 at more than one vertical location along the carrier 150 (see FIG. 1).

Referring now to FIG. 4B, with added reference to FIG. 3, with the gun assembly 101 in position, a perforating application may be triggered from surface equipment at the oilfield 301. The embodiment of FIG. 4B depicts one shaped charge jet 425 emerging from a charge 125 of the assembly 101 so as to form a discrete perforation 485. Though, multiple charges 125 forming multiple perforations 480 may be triggered simultaneously via the detonation cord 140 (see FIG. 1).

Referring now to FIG. 4C, the gun assembly 101 is shown at the target location in the well 180 following the above-described perforating. In the immediate aftermath of perforating, the reactions of the reactive powder material within the charges 125 may remain ongoing. Although this may provide only a few moments of pressure inducement within the assembly 101, this may be a more than adequate timeframe to minimize gun shock of the fired assembly 101. For example, the primary reaction and perforating may be complete in a fraction of a second, perhaps a millionth or a few millionths of a second and likely at least thousands of times faster than the ongoing metal powder reaction. However, as the second reaction and pressure generation continues on for an extended moment beyond the completed primary reaction, the pressure differential between the well 180 and within the assembly 101 is minimized as indicated. Once more, as the ongoing metal powder reaction begins to taper off and extinguish, so too does the differential. That is, pressure in the assembly 101 may begin to lift the in-gun pressure in a more smoothly and equalizing manner relative the surrounding pressure of the well 180 environment (see FIG. 1).

Referring now to FIG. 5, a flow-chart is shown summarizing an embodiment of utilizing a pressure inducing charge assembly in a well. Specifically, a shape charge is configured that includes reactive metal powders. The charge is loaded into the assembly as indicated at 515. The mechanism may or may not include a primary, substantially faster reacting, explosive directed at an application. That is, as noted at 535, once the assembly is deployed into the well, the application may be triggered, generally with reliance on the primary explosive. The application may additionally expose a void or interior of the assembly to the well as indicated at 555.

In spite of the exposure of the assembly interior to the well and potentially high pressures therein, well damaging gunshock may be substantially avoided. This is due to the above noted reactive metal powders which may raise in-gun pressure at the aforementioned interior as noted at 575. Indeed, as indicated at 595, an elevated in-gun pressure is achieved and may even be maintained for a period that exceeds the relevant triggering and/or application timeframe of high pressure explosive application. Thus, measurable gunshock related damage to the well as a result of the application may be rendered even less likely.

Embodiments described hereinabove include charge assemblies for use in downhole environments in a manner that substantially avoids gunshock induced damage in the well. This may be achieved in a manner that avoids sole reliance on propellants. Thus, an effective technique for carrying out applications such as using reactive shaped charges in perforating operation may be undertaken in high differential pressure environments without a significant likelihood of follow-on high cost remedial action.

In another embodiment, the disclosed technique is used in perforating for hydraulic fracturing operations. Thus, a substantial increase in gun pressure may be obtained such that the wellbore pressure will also be substantially increased. This leads to creating fractures in the formation near the wellbore region when at least one perforation exists on the casing 480 near the perforating gun assembly 101.

The preceding description has been presented with reference to presently preferred embodiments. Persons skilled in the art and technology to which these embodiments pertain will appreciate that alterations and changes in the described structures and methods of operation may be practiced without meaningfully departing from the principle, and scope of these embodiments. For example, techniques detailed herein may be utilized in open-hole environments, or as a manner by which to enhance perforating depth and character irrespective of gunshock minimization. Furthermore, the foregoing description should not be read as pertaining only to the precise structures described and shown in the accompanying drawings, but rather should be read as consistent with and as support for the following claims, which are to have their fullest and fairest scope. 

We claim:
 1. A charge assembly of a downhole tool for deployment in a well, the assembly comprising: a carrier housing defining an in-gun void space therein; and a shape charge accommodated by said carrier housing, said charge comprising a reactive metal powder for elevating an in-gun pressure in the void space during an application in the well by the tool.
 2. The assembly of claim 1 wherein said charge further comprises an explosive for exposing the void space to the well.
 3. The assembly of claim 2 wherein a reaction of the explosive is a detonation reaction and a reaction of the reactive metal powder exceeds the detonation reaction in duration.
 4. The assembly of claim 2 wherein the tool comprises a perforating gun.
 5. The assembly of claim 1 wherein said charge is dedicated to the inducing in a manner of non-exposure of the void space to the well.
 6. The assembly of claim 1 wherein said charge is a first charge dedicated to the inducing in a manner of non-exposure of the void space to the well, the assembly further comprising a second shaped charge with an explosive for exposing the void space to the well during the application.
 7. An in-gun pressure inducing shaped charge for incorporation into a perforating gun assembly for a perforating application at a target location in a well, the charge comprising: a charge case; a retained material within said case; and a liner over said material to form a perforating jet, one of said case, said material and said liner comprising a reactive metal powder for inducing in-gun pressure in a void space of the assembly during the application.
 8. The mechanism of claim 7 wherein the reactive metal powder is a mixture of a constituents comprising a metal, a metal oxide, a metal carbonate and a metal nitrate.
 9. The mechanism of claim 8 wherein the reactive metal powder comprises at least about 5% of each of the constituents.
 10. The mechanism of claim 8 wherein the metal is selected from a group consisting of aluminum, beryllium, titanium, tantalum, yttrium and zirconium.
 11. The mechanism of claim 8 wherein the metal oxide is one of a bismuth, cobalt, chromium, copper, iron, iodine, manganese, nickel, lead, strontium and tungsten based metal oxide.
 12. The mechanism of claim 8 wherein the metal carbonate is one of a barium, calcium, magnesium, potassium, lithium and strontium based metal carbonate.
 13. The mechanism of claim 8 wherein the metal nitrate is one of a nitrogen oxide based barium, calcium, lithium, potassium, magnesium and strontium.
 14. The mechanism of claim 7 wherein the other of said case, said material and said liner is of a reactive powder for exposing the void space to the well during the application.
 15. The mechanism of claim 14 wherein the explosive is selected from a group consisting of a metal, a metal based oxide carbonate and a metal based oxide nitrate.
 16. A method of performing an application at a target location in a well, the method comprising: deploying an application tool to the target location, the location of a given pressure; triggering the application, said triggering comprising exposing a void space of the tool to the given pressure; and increasing a pressure in the void space in conjunction with said triggering, the void space of a pressure below the given pressure in advance of said increasing.
 17. The method of claim 16 further comprising increasing a pressure in the wellbore in conjunction with said triggering for a hydraulic fracturing application.
 18. The method of claim 16 further comprising maintaining said increasing for a period exceeding a duration of said triggering.
 19. The method of claim 16 further comprising equalizing the pressure in the void space relative the given pressure in a manner substantially avoiding shock related damage to the well from the application.
 20. The method of claim 16 wherein said increasing comprises generating one of gas and heat reactive metal powder of a shaped charge adjacent the void space.
 21. The method of claim 21 wherein said triggering further comprises utilizing an explosive of the shaped charge for the exposing. 